The spliceosome as a transposon sensor.

Area of Science:

• Molecular Biology
• Genetics
• Immunology

Background:

• Eukaryotes possess RNA silencing pathways to differentiate self from non-self nucleic acids, crucial for suppressing mobile genetic elements and maintaining genome integrity.
• While RNA silencing machinery is well-studied, the precise mechanisms for self/non-self discrimination remain largely unknown.
• These pathways are conserved across eukaryotes, from protists to humans.

Purpose of the Study:

• To elucidate the mechanisms by which RNA silencing pathways distinguish self from non-self nucleic acids.
• To investigate the role of gene expression characteristics, such as intron properties, in RNA silencing.
• To explore the potential involvement of the spliceosome in small RNA biogenesis and genome defense.

Main Methods:

• Analysis of RNA silencing pathways in the yeast Cryptococcus neoformans.
• Examination of intron sequences and spliceosome stalling in transposon-derived transcripts.
• Comparative literature review of small RNA pathways (siRNA and piRNA) in plants and animals.

Main Results:

• Transposon-derived transcripts in C. neoformans were found to contain suboptimal introns.
• These suboptimal introns caused transcripts to stall in spliceosomes, promoting the generation of small interfering RNAs (siRNAs).
• This process identified gene expression signal strength as a metric for distinguishing foreign elements from host genes.

Conclusions:

• The spliceosome and intron properties play a novel role in genome defense by guiding small RNA biogenesis.
• Gene expression signal strength serves as a key indicator for identifying non-self nucleic acids.
• Evidence suggests the spliceosome may similarly guide small RNA biogenesis in siRNA and piRNA pathways across diverse eukaryotic systems, including plants and animals.